Les Chenilles Processionnaires

Look up into the pine trees of the P-O in February/March and you cannot fail to notice the light coloured, web-like cocoons swinging from the tree tops.

Pine caterpillars
Falgos Golf Course – by Susan Wager

Chenillles processionairesChenillles processionairesThese are in fact caterpillar nests, constructed by the ‘chenille processionnaire’ larva, who  live in large ‘tents’ and march out at night in single file (hence the name) to feed on the pine needles.

They leave  behind them a pheromone trail (a kind of chemical message), which enables them to find their way back to the nest after feeding.

The pine processionaries have few natural predators and even birds rarely eat them because of their toxic and unpleasant tasting hairs.

The forestry commission (Office National des Forêts) sprays the trees by helicopter every year, with an insecticide that is harmless to animals and humans. This usually takes place in October.

French naturalist, Jean Henri Fabre arranged a group of these caterpillars into a complete circle around the edge of a flowerpot to test out their urge to follow each other in a single-file head-to-tail line. They followed each other round in a circle for seven days!

If you have nests on your property, you are advised to cut off the branch of the tree and burn the nest. If the property has a large quantity of nests, ask advice at your local mairie, who may be able to arrange spraying.

Chenilles Processionnaires

Chenilles Processionnaires

You can also now buy (or make) an environmentally-friendly trap which apparently works very well. Fix a bag containing earth to the trunk of the tree with some kind of collar to channel the caterpillars into the bag. When they leave their nests to feed, follow-my-leader style, they should drop into the bag, which you should check every day and dispose of with care. The expert advice is to burn once they’re in.

Which ever option you choose, do take care.

Quite apart from the damage caused to the trees, the caterpillars have fine hairs on their back containing a protein which causes severe irritation and dermatitis, and in some cases an allergic reaction (anaphylactic shock) to both humans and animals.
Even after the caterpillar is dead, the hairs remain toxic. Take care when walking your dog in areas where the caterpillars may be, or have been.

Initial symptoms to watch out for in your pet may include vomiting and tongue swelling.

pine proIf you suspect that your pet has come in contact with them, you should immediately consult your nearest vet.

If you are not able to do this quickly, you should flush the dog’s mouth with plenty of water, taking care to keep the head down so the hairs don’t move towards the throat.

Remember that the poison is also harmful to humans, so wear protective gloves – but still do all you can to get your pet to a vet.

Here are some homeopathic treatments suggested by a vet if you are out in the middle of nowhere and no professional treatment is quickly available. Carry them around with you..

♦ Poumon histamine 3 ou 5ch – 3 granules (for respiratory allergies)
♦ Apis mellifica 3 ou 5 ch – 3 granules (for insect bites causing swelling)
♦ Belladonna 9CH – 5 granules / toutes les heures (fever, bruising…)

Give again every 15 minutes until you find a vet.
These are NOT  a substitute for veterinary treatment.



  1. Prophylactically I received cortison supositories from my vet, which I always carry with me when I walk my dog. In case of contact with the caterpillars the suppositories are a first aid to prevent an allergic shock, and help to bridge the time till you get to the vet.

  2. Like the new format, click more to read articles of interest.
    Varied and interesting as usual. Well done team.

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